Lubrication system for a differential

ABSTRACT

A differential having a lubrication system for supplying lubricant to the interior of the rotating differential carrier both at high and low rotative speeds. An axleway is provided in the carrier along its axis of rotation and a first bore forms that portion of the axleway adjacent the carrier&#39;&#39;s inner cavity. Cups are provided around the carrier&#39;&#39;s exterior and fluid passages extend radially through the carrier from these cups into the axleway to a radius less than the radius of the first bore.

United States Patent [191 Lindenfeld et al.

[ June 26, 1973 LUBRICATION SYSTEM FOR A DIFFERENTIAL Inventors: John A.Lindenfeld, St. Joseph,

Mich; Cledlth L. Hartz, South Bend, lnd.; North A. Shelly, Niles, Mich.

Clark Equipment Company, Buchanan, Mich.

Filed: Apr. 29, 1971 Appl. No.: 138,514

[73] Assignee':

US. Cl. 184/11 A, 184/6.12, 192/113 B Int. Cl. F1611 7/16 Field ofSearch 192/113 B; 18416.12,

[56] References Cited UNITED STATES PATENTS 7/1962 Bixby 184/612 6/1964Dames et al 184/11 A i i a 3,474,888 10/1969 Carlson et al 192/113 B3,448,635 6/1969 Nelson l84/6.12 X 3,590,954 7/1971 Plantan 184/6.122,935,889 5/1960 Adams et al. 192/113 B X Primary ExaminerManuel A.Antonakas Attorney-Kenneth C. Witt, John C. Wiessler, Robert H. Johnson,Lewis J. Lamm and Robert J. Norton [57] ABSTRACT A differential having alubrication system for supplying lubricant to the interior of therotating differential carrier both at high and low rotative speeds. Anaxleway is provided in the carrier along its axis of rotation and afirst bore forms that portion of the axleway adjacent the carriers innercavity. Cups are provided around the carrier's exterior and fluidpassages extend radially through the carrier from these cups into theaxleway to a radius less than the radius of the first bore.

13 Claims, 3 Drmving Figures PAIENIEUJUIIZS ms v3.7%]..343 I saw 1 or 2INVENTORS NOAH A. SHEALY JOHN A. LINDENFELD y CLEDITH L .IHARTZ ATTORNEYLUBRICATION SYSTEM FOR A DIFFERENTIAL BACKGROUND OF THE INVENTION Thisinvention relates to the lubrication of differential mechanisms such asare employed in vehicle final drives to divide and transmit torque tothe driving wheels of the vehicle. The various gears and othercomponents of such mechanisms must be cooled and lubricated at all timesduring the mechanisms operation by an adequate flow of oil and typicallysuch flow is accomplished by sealing the rotating carrier of thedifferential withina housing partially filled with oil so that therotation of the carrier may be employed to circulate the oil. The designof such lubrication systems usually takes one of two forms dependingupon the intended use of the differential and therefore upon theexpected normal rotative speed of the differential carrier. If thecarrier is to be normally operated at relatively high rotative speeds itis common to supply oil to the carrier near its axis of rotation so thatcentrifugal forces may be utilized to urge the oil to flow radiallyoutward through passages in the carrier directing the oil to thecarriers internal components, but if the carrier is to be normallyoperated at relatively low rotative speeds it is common to providescoops or cups around the carrier to lift oil upward as the carrierrotates so that it may drain radially inward by gravity through passagesin the carrier directing the flow to the carriers internal components.Since centrifugal forces urge oil to flow outwardly at high rotativespeeds and gravitational forces urge oil to flow inwardly at lowrotative speeds, a lubrication system designed for low speed operationwill not provide an adequate supply of oil to the carriers internalcomponents when the carrier is operated at high speeds because oilcannot flow inwardly through the radial passages against the centrifugalforces which predominate at such speeds. Conversely, a lubricationsystem designed for high speed operation will not provide an adequatesupply of oil to the carriers internal components when the carrier isoperated at a low speed because the centrifugal forces at such speedsare not sufficient to urge oil to flow radially outward through thecarriers lubricating passages. Further, if a differential carrierincorporates both the usual high and low speed lubrication systems theradial passages of the low speed system operate 'to bleed oil outwardlyfrom the high speed system during high speed operation, and therefore aninsufficient quantity of oil will be supplied to the carriers internalcomponents during high speed operation.

It is an object of the present invention to provide a lubrication systemfor a differential which provides an adequate supply of lubricatingfluid to the internal components of the differential carrier regardlessof the rotative speed at which the carrier operates.

SUMMARY OF THE INVENTION In carrying out our invention in one preferredembodiment thereof, we provide a lubrication system for a differentialcarrier having an inner cavity and an axleway into the inner cavityalong the carriers axis of rotation. The lubrication system includes afirst bore forming that portion of the axleway adjacent the carriersinner cavity and fluid passages extending radially through the carrierto open into the axleway at a radius less than the radius of the firstbore. Circumferentially spaced holding chambers are provided in thecarrier which are open into the axleway and are connected by the firstbore to the carriers inner cavity, the radial fluid passages extendinginto the axleway angularly between these holding chambers and thechambers having an outer surface whose radius is greater than the radiusof the first bore. A second bore having a radius less than the radius ofthe first bore forms that portion of the axle-way adjacent the exteriorof the carrier and extends into the holding chambers to connect thesechambers with the exterior.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 illustrates a differential,partially in section, having a lubrication system in accordance with anembodiment of this invention,

FIG. 2 is an enlarged sectional view along line 22 of FIG. 1 and showingto advantage a portion of the lubrication system, and

FIG. 3 is an enlarged section view along line 33 of FIG. 1 and showingto advantage another portion of the lubrication system.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, a differentialmechanism embodying this invention is indicated generally by the numeral10. A differential housing 12 contains the various components of thedifferential and provides openings for an input'shaft 14 and a pair ofcoaxial drive axles 16L and 16R. Input shaft 14 is rotatablyjournaledwithin housing 12 upon a bearing 18 and a pair of thrust bearings 20,and a driving pinion gear 22 is splined for conjoint rotation with theinput shaft. A ring gear 24 is driven by driving gear 22 and isconnected, as by bolts 26, to rotate a differential carrier 28 about itsaxis of rotation defined by tapered thrust bearings 30L and 30R.Differential carrier 28 is hollow and generally closed and carries across 32 disposed diametrically across its inner cavity 34, the ends ofcross 32 being received within diametrically opposed bores 36 and 38formed in carrier 28 to fix the cross'for rotation with the carrier.Each shaft of cross 32 carries a pair of planetary pinion gears 40journaled radially outward near the opposite ends of the shafts andthese planetary gears each engage both a side gear 42L and a side gear42R to complete the differential gear train. Axles 16 extend intodifferential carrier 28 through axleways 17 formed in the carriercoaxial with its axis of rotation and the axles are splined at 19 forconjoint rotation with their respective side gear.

Differential 10 may also include means for resisting the freedifferential action of the mechanism to a limited extent so that sometorque may be exerted by one drive axle even if the other axle ispermitted to turn free. Such resisting means is provided by a clutchpack 44L associated with axle 16L and a similar clutch pack 44Rassociated with axle 16R, each clutch pack including a plurality ofannular friction discs 46 splined to carrier 28 for rotation therewiththat are interleaved with a plurality of annular friction discs 48splined for rotation with their respective side gear'42. When axles 16Land 16R are operating at the same rotative speed there is no relativerotation between differential carrier 28 and either side gear 42L or42R, and therefore no relative rotation between the interleaved frictiondiscs of either clutch pack. However, if one axle 16L or 16R ispermitted to turn more freely than the other, relative motion betweenits respective side gear 42 and carrier both"relatively 'high rotati ve'spas-ta I a low rotative speeds, and further since thepredominatres ,will against i A lubrication systern isp v iided for differe insure theproper lubrica rijof thei various components'and to alsoflprovide meansfor dissipating al gnant; m1

oil orsor neothe i d p i i d tained within the on ihgin sufficientquan"ty tofo'rm tion. Although these twoiportions of thelubricatiorisystem operate in concert and include common ele-i ments they willbedescribed separately for clarity. i

As ring gear 24 rotates during highspeed operation -1 of differential l0thesurface of the ring gearxisbathed l in oil as it passes throughlubricant reservoir 50. Sur face tension causes'a film of oil to clin gtojthe surface of ring'gear 24 as it rotates out of the lubricant reservoir and if the rotative speedfof gear 24 is sufficiently high a portionof thiso il film will bef thrownradially outward from the gearbycentrifugal force to impinge upon the inner wall 52 of differentialhousing 12 around its entire upper periphery. Some of the oil thrownfrom ring gear 24 will be collected byagutter 1 or trough or channel54which extends inwardly froml w housing inner wall 52and slantsdownwardly toward axle 16R from above r inggear24'so that theoil socollectedwill be urged by gravity to flow toward the inlet 56 of apassage 58R formed in housing 12' and vfor-thing a continuation of thechannel 54. Passage 58R; extends f through differential housing 12 in adownward dir'ection and the oil entering passageinlet 56 is urgedb ygravity to flow through the passage and fill a eir cuinfera entialgroove 60 formedin housing 12 tosurroundrotating axle 16R withoil,Awiper 62 prevents the loss of oil outwardly from differentialhousingflll around axle 16R, but thejaxle increases in diameter inwardlyfrom thevicinity of groove 60 toward sidegear 42R and thereforeoil isurged'by centrifugal force to flow 1= axially inward into axleway 17Rthrough an annular space between axle 16R and a bore 66R in carrier 28which forms the outer portion of axleway 17. A plurality ofcircumferentially spaced holding chambers 68R in differential carrier 28open into axleway 17 to receive the oil from bore 66 and each holdingchamber 68 is the outer portion of a sector of a truncated cone limitedby the diameters of the various passages or openings into these chambersand oil will overflow out of the chambers into the passage with thegreatest diameter since this passage will have the lowest effectiveclutch pack 44 Rjinay be collected ingrooveI78R to luv bricate the teethof sidegear 42R and pinion gear-s40 d v d andthereafter floodinnercavity 34 ofthe differential carrier withoilJSuitable openings, asindicated at 80,- ,1 are proyidedfin differential carrier 28 to permitoilto exit from inner cav ty vj34 and return to reservoir 50Axle-;l6L;andit s associated side gear-42L. and clut eh; pack 44L arecooled and lubricated during high speed i operationofdifferentiallt) inamanner similar to that explained vabove for: lubricating thecorresponding j "1 components associatedwithaxle 16R. As ring gear 24rotatesoutoflubricant pool 50 a portion ofthe oil film g d which clingsto thering gears surface is notthrown i outwardlyffrom the gear'but israther carried-by ring 1 gear 24mm itsmeshwithdrivepinion zzgwhempohsome of thisoil'is scrapedfrom ring gear 24on to the fasterturning drivepinion22. A partial cover plate or flzwn rm nsw t mper b vdr l i i"-fion"2 2jis supperted from inner wall 52 of differential i housing 12and covers a substantial portion oft-lie drive pinionfs peripherysothatoil thrown outwardlyby centrifugal force from drive pinion 22 iscollected upon-the inn'erwallof shield 82; A window 84 is provided inshield82 near its greatest diameter and the nat ural pumpingfactionofdrive pinion 22 urges the oil colv lecteduponthe innervvallof shield82'to'flowtow ard window 84 and outwardly therefrom. Asecond gutter ortrough eanness; whichis similar to trough 54 1 previoiisiyexplained,extends inwardlyfromdifferen-w tial housingitlilel'dwttlislhhd is locatedtoreceiveor 1 catch the oildischargedifromwindow 84. Trough. i j slants downwardly toward axle: 16L'and,f nnelsintola LpasSagejSSL inhoiisingIZ similar to passage SSRprevi-Y ouslyexplained so that oil within the trough is urged by gravity to flowthrough passage SSL and surround axle 16L with oil. Axle-way 17].. isformed by elements allochirally similar to those forming axleway 117Rand therefore oilis urged to pass inwardly through theaxleway in jthemanner previously explainedto cool and lua bricate clutch pack 44L andside gear 42L.

Duringthe operation of differential 10*at differentials lubrication inthe manner previously explained. In order to lubricate the componentsassociated with axle16L during such low speed operation a plurality ofoppositely orientated dippers or cups, such v relatively d low rotativespeed, the peripheral velocityof ringgear y 24 anddrivepinionZZ arenotsufficientitotlirow any I quantityflofoil outwardlyftherefrom andtherefore? i troughs54and86 donot receive sufficien toil for the as cup88L, are formed around carrier 28 to rotate downward into lubricantreservoir 50, fill with oil, and lift such oil upward so that it maydrain by gravity through passages 90L on to axle 16L. Referring to FIG.2 in conjunction with FIG. 1, differential carrier outer surface 92cooperates with a wall 94 extending radially from the outer surface andthen turning circumferentially to form a bowl 96 which may fill with oilwhen cup 88L is dipped into lubricant reservoir 50. As cup 88L rotatesupward out of the reservoir an amount of oil is lifted within bowl 96above a horizontal plane and is thereafter urged by gravity to enterpassage 90L through its inlet 98 located near the bowls bottom.-

Passage 90 extends inwardly through carrier 28 angularly between holdingchambers 68 in substantially a radial direction and opens at itsradially inner end 100 into a bore 102 which forms a part of axleway 17Land is coaxial with axle 16L so' that oil from the cup may draindirectly on to the axle. After draining on to the top of axle 16 thelubricating oil flows downwardly around the axle and inwardly throughbore 74L (FIG. 1) to lubricate clutch pack 44L and side gear 42L bygravity flow through the grooves and passages previously explained.

Low speed lubrication and cooling of axle 16R, clutch pack 44R, and sidegear 42R is accomplished in a manner similar to that explained above forlow speed lubrication of the corresponding components associated withaxle 16L. Referring to FIG. 3 in conjunction with FIG. 1, a plurality ofcups, such as cup 88R, are formed in carrier 28 around ring gear 24. Anopening 104 in the side of ring gear 24 permits oil to flow into bowl96R of cup 88R when the cup is dipped into lubricant reservoir 50 and apassage 90R, similar to passage 90L, opens into bowl 96R near itsbottom. Passage 90R extends inwardly through carrier 28 angularlybetween holding chambers 68 in substantially a radial direction andopens at its radially inner end 100 into a bore 102 which forms a partof axleway l7 and is coaxial with axle 16R so that oil may draindirectly on to the axle when cup 88R is lifted above a horizontal plane.After draining on to the top of axle 16R the lubricating oil flowsdownwardly around the axle and inwardly through bore 74R (FIG. 1) tolubricate clutch pack 44R and side gear 42R by gravity flow through thegrooves and passages previously explained.

Passages 90 are open at their inner ends 100 into axleways l7 and,because centrifugal force urges oil to flow outwardly through thesepassages during high speed operation of differential 10, the passagescould permit oil to drain from chambers 68 without flowing inwardthrough bore 74 for the desired lubrication of clutch packs 44 and sidegears 42. In order to prevent such a loss of lubrication during thedifferentials high speed operation the radii of passage inner ends 100are selected to be less than the radius of bore 74 so that as oil entersholding chambers 68 and pools around the chambers outer surface 70 itwill overflow into bore 74 before its radial depth is sufficient topermit the oil to be thrown outwardly through passages 90. The radii ofpassage inner ends 100 may further be a selected incremental amount lessthan the radius of bore 74 so that the quantity of oil supplied throughbore 74 may be While we have described and illustrated herein onepreferred embodiment of our invention, it will be appreciated thatmodifications may be made therein which fall within the spirit and scopeof our invention.

We claim:

1. A lubrication system for a differential having a housing defining areservoir for oil, and having rotating gearing with internal spacesincluding elements to be lubricated, the gearing also having axlewaysleading from the internal spaces axially outwardly and terminating inthe housing, axles in the axleways and dimensioned for forming passagestherearound in the axleways, the gearing including at least one memberof sufficiently great diameter to extend into the oil in the reservoir,

said lubrication system comprising, in combination,

means forming channels receiving oil thrown by centrifugal force at highspeeds from said one member, operative for directing it to the axiallyouter ends of the said axleways and continuously so directing it so thatsufficient pressure is developed in the oil to force it axially inwardlythrough the axleways into the internal spaces,

and said one member having cups with radially outer portions open to theinterior of the housing and positioned for receiving oil from thereservoir when the cups are lowermost, and radially inner portionsgenerally closed to the interior of the housing and capable of carryingoil upwardly on rotation of said one member,

said one member also having generally radial gravity passages from theclosed inner portions of the cups to the axleways operative forconducting oil from the cups to the axleways when the cups are uppermostand the oil flows downwardly by gravity, at low speeds, said internalspaces extending radially outwardly beyond the radially inner ends ofthe gravity passages, whereby oil will flow by gravity from the axlewaysinto the lower portions of said internal spaces.

2. A lubrication system according to claim 1 wherein said axlewaysinclude portions leading into said internal spaces that are positionedradially outwardly beyond the radially inner ends of the gravitypassages, whereby at high speeds oil is thrown by centrifugal forcethrough said portions of the axleways to the exclusion of forcing itradially outwardly through said gravity passages.

3. A lubrication system according to claim 1 wherein the axles increasein diameter proceeding in axially inward directions, tending to increasecentrifugal force action on the oil and thereby increasing the pressureforcing the oil axially inwardly toward the internal spaces.

4. A lubrication system according to claim 3 wherein the axlewaysinclude at least portions leading into the internal spaces that aredisposed at progressively greater radial distances than the axiallyouter ends of the axleways, whereby to increase centrifugal force inpositions progressively axially inwardly in the axleways.

5. A lubrication system according to claim 4 wherein the gearingincludes spaces co-axial with and forming portions of the axleways thatare in the shape of truncated cones with large bases directed axiallyinwardly toward said internal spaces.

6. A lubrication system according to claim 1 wherein said axlewaysterminate axially outwardly adjacent the sides of the housing, saidchannels are defined partially by the innersurface of the housing; andthe channels it the ring gear carrier furtherincluding; cups 35a: 5 I i*contin 1e along the housing tothe axially outer endsof Y the ax eways.i

one sideof the housingandinto theeorresronding lewayb it n i n n theilubrication syst meansforming cha thrownby centrifu speeds andcondueting force radiallybutwardlyainl oseannularspaees 1 oil from saidannul r spaaes' andyconductmg t ioned for entering into? oil in thereservoir andopw I r r i jfinerativeatiowlspee 7. A"lubrication systernaccording to claim 1 where iuu andern tyih said one'rnemberincludes aringgeanandthe ringgear 95 i j t y ink)831d aiflnulai spad throwsioil bycentrifugalflforcefinto" said channelsx on g Y imgfldhQwh gaidmghi ig110x28 lubricatioiilisystemiiaccording m claim w v r a a 1whereinsaidcircumferent'algroo esareofsucha rial A lubrication sy tem accq d s t "qi ts fl sextemas to"encom assrsuummiany najr saidannular the gearingincludesa drivingpinion gear in inesh with i r nd aidme hi g faf a f thering gear, andthe pin on s t s l y snt if 1111i; A lubrication Systemaccordingft ugal force into saidchannels on the side ofethe housingwherein the housingdn clude s oppositefsid e portions PP P whlchoflls'thmlm by W i and means in those portionsflorming bearings foroppolubncfmon for a f 'f site ends of said carrier, said channelsfollowalong the defimllg a 53 forolli anihavmg wtafimg inner surfaces ofthe housing and through said side p on gearmg, g l tions of the housingand into the axleways at the inner 1 the gearmkmcludmg g a d a Gamer rsurfaces of the housing defined by said side portions;

gear s dlmensmmd for emermg l 12. In adifferentialhaving a stationaryhousing defining a reservoir foroil, and including gearing in thehousing capable of being rotated at low speed, the gearing havinginternal spaces and elements in those spaces to be lubricate d,thelgearin gincluding aring gearand carrier therefor, f' a 1 i alubrication system comprising, I r structure in the carrier definingcupsfeachihavingmv into oil in thereservoir, v a i a i the ring gearcarrier defining a central cavity and ax- 20 leways leading therefromoutwardly to adjacent the sides of the housing, 7 r a thegearingincludingopposed side gears in the cavity', and axles intheaxleways connected with the side gears for rotation therewith, V V gy 25 the gearing additionally including pinion gears in the] r n i r a r.r

cavity in mesh with the side gears, thecarrier and gi f y out? a t? sidegears being dimensioned for defininganannu it r we y miter 9 f 9 F q i a3 lar space between the carrier and eachside gear; h y "QFlF WWYY andthe gearinginclu din a clutch pack inea'cho f 'f eaqhbowl, 0 w m?! Pthose annular spaces, C

of the axlewaysnj whereby p forcing the oil aitiallyfinwardly t oug nway g the 3 axlewaysfijccmmunicattng wit spaces andeffectiyerforcondueti g annular spaces wherebyltheoilflowsby through theclutch packsf f the carrier haying circujrnferentialgropyes

1. A lubrication system for a differential having a housing defining areservoir for oil, and having rotating gearing with internal spacesincluding elements to be lubricated, the gearing also having axlewaysleading from the internal spaces axially outwardly and terminating inthe housing, axles in the axleways and dimensioned for forming passagestherearound in the axleways, the gearing including at least one memberof sufficiently great diameter to extend into the oil in the reservoir,said lubrication system comprising, in combination, means formingchannels receiving oil thrown by centrifugal force at high speeds fromsaid one member, operative for directing it to the axially outer ends ofthe said axleways and continuously so directing it so That sufficientpressure is developed in the oil to force it axially inwardly throughthe axleways into the internal spaces, and said one member having cupswith radially outer portions open to the interior of the housing andpositioned for receiving oil from the reservoir when the cups arelowermost, and radially inner portions generally closed to the interiorof the housing and capable of carrying oil upwardly on rotation of saidone member, said one member also having generally radial gravitypassages from the closed inner portions of the cups to the axlewaysoperative for conducting oil from the cups to the axleways when the cupsare uppermost and the oil flows downwardly by gravity, at low speeds,said internal spaces extending radially outwardly beyond the radiallyinner ends of the gravity passages, whereby oil will flow by gravityfrom the axleways into the lower portions of said internal spaces.
 2. Alubrication system according to claim 1 wherein said axleways includeportions leading into said internal spaces that are positioned radiallyoutwardly beyond the radially inner ends of the gravity passages,whereby at high speeds oil is thrown by centrifugal force through saidportions of the axleways to the exclusion of forcing it radiallyoutwardly through said gravity passages.
 3. A lubrication systemaccording to claim 1 wherein the axles increase in diameter proceedingin axially inward directions, tending to increase centrifugal forceaction on the oil and thereby increasing the pressure forcing the oilaxially inwardly toward the internal spaces.
 4. A lubrication systemaccording to claim 3 wherein the axleways include at least portionsleading into the internal spaces that are disposed at progressivelygreater radial distances than the axially outer ends of the axleways,whereby to increase centrifugal force in positions progressively axiallyinwardly in the axleways.
 5. A lubrication system according to claim 4wherein the gearing includes spaces co-axial with and forming portionsof the axleways that are in the shape of truncated cones with largebases directed axially inwardly toward said internal spaces.
 6. Alubrication system according to claim 1 wherein said axleways terminateaxially outwardly adjacent the sides of the housing, said channels aredefined partially by the inner surface of the housing, and the channelscontinue along the housing to the axially outer ends of the axleways. 7.A lubrication system according to claim 1 wherein said one memberincludes a ring gear, and the ring gear throws oil by centrifugal forceinto said channels on one side of the housing and into the correspondingaxleway.
 8. A lubrication system according to claim 7 wherein thegearing includes a driving pinion gear in mesh with the ring gear, andthe pinion gear throws oil by centrifugal force into said channels onthe side of the housing opposite that into which oil is thrown by thering gear.
 9. A lubrication system for a differential having a housingdefining a reservoir for oil, an having rotating gearing, the gearingincluding a ring gear and a carrier therefor, the ring gear geingdimensioned for entering into oil in the reservoir, the ring gearcarrier defining a central cavity and axleways leading therefromoutwardly to adjacent the sides of the housing, the gearing includingopposed side gears in the cavity, and axles in the axleways connectedwith the side gears for rotation therewith, the gearing additionallyincluding pinion gears in the cavity in mesh with the side gears, thecarrier and side gears being dimensioned for defining an annular spacebetween the carrier and each side gear, and the gearing including aclutch pack in each of those annular spaces, the lubrication systemcomprising, in combination, means forming channels positioned forreceiving oil thrown by centrifugal force by the ring gear at highspeeds and conducting it to the axially outer ends of the axleways,whereby pressure deVelops for forcing the oil axially inwardly throughthe axleways, the axleways communicating with said annular spaces andeffective for conducting oil into those annular spaces whereby the oilflows by centrifugal force radially outwardly in those annular spacesthrough the clutch packs, the carrier having circumferential groovesreceiving oil from said annular spaces and conducting it to the meshingareas between the pinion gears and the side gears and into a centralspace in the cavity, the gearing also including passages from saidcentral space to the reservoir, the ring gear carrier further includingcups positioned for entering into oil in the reservoir and operative atlow speeds for picking up oil and carrying it up and emptying it wherebythe oil flows by gravity into said annular spaces and onto the clutchpacks therein, and into the said meshing areas.
 10. A lubrication systemaccording to claim 9 wherein said circumferential grooves are of suchaxial extent as to encompass substantially all of said annular spacesand said meshing areas.
 11. A lubrication system according to claim 9wherein the housing includes opposite side portions and means in thoseportions forming bearings for opposite ends of said carrier, saidchannels follow along the inner surfaces of the housing and through saidside portions of the housing and into the axleways at the inner surfacesof the housing defined by said side portions.
 12. In a differentialhaving a stationary housing defining a reservoir for oil, and includinggearing in the housing capable of being rotated at low speed, thegearing having internal spaces and elements in those spaces to belubricated, the gearing including a ring gear and carrier therefor, alubrication system comprising, structure in the carrier defining cupseach having a radially outer open end, and wall elements at its radiallyinner end forming a bowl, the structure further having a passage leadingradially inwardly from each bowl to the internal spaces, the cups beingpositioned radially outwardly sufficiently that at least the outer openends thereof extend into the oil in the reservoir when the cups aredirected downwardly, the cups being operative, at low speed of rotationof the carrier, for picking up oil from the reservoir and, as the cupsprogress upwardly from downward position toward horizontal position, forholding oil in the bowls and, as they progress further and said passagespass above the horizontal, the oil in the bowls flows through thepassages into said internal spaces.
 13. A lubrication system accordingto claim 12 wherein the internal spaces and the elements therein includeportions distributed angularly around the central axis of rotation, andfurther wherein the cups are also distributed angularly around thataxis.